1. Field of the Disclosure
This disclosure relates to a liquid crystal display (LCD) device, and more particularly to an LCD device capable of being divisionally driven using an edge type backlight unit.
2. Description of the Related Art
Currently, the application fields for liquid crystal display (LCD) devices are widening because of their features, such as their light weight, slimness, a low driving voltage, and so on. This trend is confirmed in the ways in which the LCD devices have been applied to office automation equipment, audio equipment, video equipment, and so on. The LCD device controls a transmitting amount of light on the basis of image signals applied to a plurality of control switches, in order to display a picture.
The LCD device, which is not self-luminescent, includes a backlight unit irradiating light on the rear surface of an LCD panel in which a picture is displayed. The backlight unit is classified as either an edge type or a direct type in accordance with the disposition of its light source.
The edge type backlight unit includes a light source which is positioned at one edge of the LCD panel. Also, the edge type backlight unit applies light emitted from the light source to the entire surface of the LCD panel through a light guide panel and a plurality of optical sheets. On the other hand, the direct type backlight unit includes a plurality of light sources arranged opposite the rear surface of the LCD panel. These plural light sources apply light to the rear surface of the LCD panel through a diffusion plate and a plurality of optical sheets.
However, since the plural light sources are arranged on a flat surface, their shapes appear on the liquid crystal panel which is disposed above the direct type backlight unit. To rectify this, a direct type backlight unit of the related art increases the distance (or gap) between the light sources and the liquid crystal panel. Also, the direct type backlight unit has to include a light disperser for entirely uniform light distribution. Accordingly, the direct type backlight unit of the related art is limited to slimness. In addition, the light output surface of the backlight unit becomes larger in size corresponding to the increased size of the LCD device. The enlarged light output surface of the direct type backlight unit can not be planarized as long as the light disperser does not have a sufficient thickness.
On the other hand, the edge type backlight unit has a disadvantage due to lower brightness because the light emitted from the light source has to penetrate the light guide plate. This results from the structure that the light guide plate disperses light from the light source which is positioned at one side of the surface of the light guide plate. Likewise, the light guide plate requires a high optical design technology and a high treatment technology, in order to uniformly distribute light.
Such direct and edge type backlight units have individual problems which are in contrast to each other. Thus, the direct type backlight units are mainly used in LCD devices in which the priority of the brightness is greater than the priority of the thickness. In contrast, the edge type backlight unit is mainly applied to LCD devices which prioritize a thin body over brightness. Therefore, in accordance with design, the LCD devices including the edge type backlight unit have been used in a notebook computer and a monitoring personal computer.
The LCD device divides a liquid crystal panel into a plurality of regions and independently drives the divided regions, in order to allow a dark portion to be more darkly displayed and a bright portion to be more brightly displayed. However, it is not easy for the LCD device including the edge type backlight unit to divisionally drive the liquid crystal panel, because the liquid crystal panel can not be divided into regions each including at least one light source. In other words, the LCD device can drive only the regions in which the light source is disposed, because the liquid crystal panel is divided into the region depending on the disposition of the light source. In view of this point, the LCD device with the edge type backlight unit is more difficult in the divisional drive mode than that with the direct type backlight unit.